R Value

A rating for the ability of a virus to spread. R of 1 would indicate each infected person infects one person. Anything higher than 1 has the potential to grow the number of cases exponentially (i.e. an outbreak or pandemic). For example, measles had an R value of 15.

This is similar to big O notation in estimating computation complexity. R1 would be constant time and R1+ would be O(N^1+).